1. Field of the Invention
This invention relates generally to a sensor for detecting the presence of defects, and more specifically, to a sensor for detecting defects in an air-frame structure by means of meandering transmission lines.
2. Discussion
It is well known that air travel puts a large amount of structural stress on air-frame structures. Since the air-frame structure is repeatedly administered to these stresses it eventually becomes very susceptible to certain defects or flaws such as material fatigue, loosened connections, delaminations, etc., thus affecting the integrity of the aircraft. In addition, flaws from in-flight incidents, such as impacts with foreign objects and battle damage, could also provide problems in maintaining the aircraft in a safe condition. If these defects go unchecked or undetected, the eventual outcome could be catastrophic. It therefore becomes crucial to at least periodically check for defects within the air-frame structure, especially at high stress or flight critical locations.
Different methods are known in the art to detect the presence of flaws in an air-frame structure. These methods have included visual inspection for observing such things as loose rivets, buckled material and dents; strain gages for detecting the presence of certain distortions in structural members; and the use of ultrasonics and acoustics for administering sound waves to detect flaws by means of determining sound transmission quality. Generally, these procedures have not met with adequate success. For instance, visual inspection is limited by human skill and other obvious physical limitations, strain gages are not practical to position throughout all panel structures of an aircraft, and ultrasonics and acoustics are difficult to instrument in certain structures. In addition, many of these prior art methods require a certain amount of expertise and technical skill to adequately implement. Further problems arise in that many of these prior art methods do not provide the capability for both the continuous or the selective, such as in-flight, detection of flaws.
What is needed then is a sensor to detect structural flaws within an air-frame structure without the need to perform a technically intricate procedure, and further, to perform the detection continuously or at a desirable time. It is therefore an object of the present invention to provide such a sensor.